1. Technical Field
The present invention relates to a liquid discharge apparatus, a control method of a liquid discharge apparatus, and a control program of a liquid discharge apparatus.
2. Related Art
A liquid discharge apparatus such as an ink jet printer forms an image on a recording medium, by driving a piezoelectric element provided in a discharge unit using a drive signal, and displacing the piezoelectric element so as to discharge liquid such as ink filling the cavity (a pressure chamber) of the discharge unit. In such a liquid discharge apparatus, abnormal discharge may occur, in which the discharge unit is not able to properly discharge the liquid, due to thickening of liquid, or bubble mixing into a cavity. Then, if the abnormal discharge occurs, it is not able to exactly form dots to be formed on a medium by using the liquid discharged from the discharge unit, and thus the quality of the image formed by the liquid discharge apparatus is reduced.
JP-A-2004-276544 proposes a technique for preventing deterioration in an image quality due to abnormal discharge, by detecting residual vibration occurring in a discharge unit after a piezoelectric element is driven in response to a drive signal, and determining the discharge state of the liquid in the discharge unit, based on the characteristics of the residual vibration, such as the period and amplitude, and the like of the residual vibration.
However, with an increase in a print speed in recent years, an interval from when a piezoelectric element is driven in response to a drive signal to when the piezoelectric element is driven next becomes gradually shorter. When the driving interval of the piezoelectric element is reduced and the period of the drive signal is reduced, a detection period is shortened, which is a period provided for detecting residual vibration during one period of the drive signal, and a period in which the signal level of the drive signal is maintained at a certain level, or a fluctuation in the signal level of the drive signal is reduced, in order to accurately detect the residual vibration. Then, when the detection period is shortened, there is a high possibility that the detection accuracy of the residual vibration is reduced, or the detection result of the residual vibration does not include the amount of information to an extent capable of identifying the characteristics of the residual vibration. In this case, there is a problem in that the accuracy of the determination is likely to decrease in the determination of the discharge state based on the characteristics of residual vibration.